There are many testing procedures known for evaluating bevel and cylindrical gears. Among these testing procedures are single flank and double flank analysis, noise and vibration testing, and, tooth contact analysis.
In tooth contact analysis, a marking compound, usually consisting of a fine chalk powder suspended in a carrier substance such as oil, is applied to the tooth surfaces of one member of a gear pair, such as the gear member of a bevel gear pair, and the pair is then run in mesh usually under a light load. The marking compound is removed from the areas of the gear tooth surfaces which contact the tooth surfaces of the mating pinion member of the gear set. The marking compound is transferred to the pinion tooth surfaces leaving a "footprint" of the contact region visible on the gear tooth surface.
In the prior art, marking compound has primarily been applied to tooth surfaces by two methods, manual brushing or spraying. In the manual brushing method, marking compound is hand brushed onto tooth surfaces. While hand brushing produces an adequate coating, this procedure is very time consuming. Also with hand brushing, gear-to-gear consistency of coating is difficult to maintain.
Spraying methods and systems, such as shown in U.S. Pat. No. 5,373,735 to Gutman for example, are relatively fast and provide a more even coating of tooth surfaces. However, spraying also results in marking compound being sprayed onto other machine components in the testing machine chamber as well a contaminating mist being formed in the atmosphere of the testing chamber and thus a mist collector is usually required to meet environmental standards.
Another disadvantage of spraying is the necessity of utilizing a carrier oil having a low viscosity in order to perform the spraying process. The higher the viscosity of the carrier oil, the thicker it is and the more difficulty it presents in flowing through the spraying mechanism. However, while lower viscosity oils flow adequately through the spraying mechanism, the thin consistency of the oil promotes a marking compound that does not adhere well to the tooth surfaces but instead tends to run down the tooth surface and may result in producing a smeared tooth contact pattern.
Yet a further disadvantage of spraying, and also hand brushing to a lesser extent, is that a gear set which has been roll tested previous to the application of marking compound, as is common, will likely have oil on the tooth surfaces as a result of the roll test. Spraying marking compound on these oily tooth surfaces will lead to further thinning of the marking compound due to the oil on the tooth surfaces mixing with the carrier oil of the marking compound. While hand brushing enables the use of a higher viscosity carrier oil than in spraying processes, the consistency of the marking compound is still adversely affected by the presence of oil on the tooth surfaces.
Prior to the application of marking compound, residual oil on the tooth surfaces may be removed. One popular method if to utilize a high pressure air spray to blow oil off the tooth surfaces. While this procedure does remove some oil, a coating of oil on the tooth surfaces still remains. Another procedure is to remove and wash the gear which results in all oil being removed but this method is very time consuming and does not fit well into production line situations.
Thus, there remains a need to provide a marking compound application system free of the disadvantages of the prior art methods discussed above. Therefore, it is an object of the present invention to provide a marking compound application system and method which retains rapidity of application and consistency of coating while confining application of marking compound to tooth surfaces and enabling the testing chamber atmosphere to remain free of marking compound mist contamination. With the present invention, the need and expense of a mist collector system to capture marking compound from a contaminated atmosphere is avoided.
It is another object of the present invention to provide a consistent gear-to-gear coating and to enable marking compound to be applied to tooth surfaces even in the presence of residual oil from a previous process.